Packetizing media for a time slotted communication system

• US 20070053373A1
• Filed: 09/02/2005
• Published: 03/08/2007
• Est. Priority Date: 09/02/2005
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: FitzGerald, Cary, Robison, Helen
• Granted Patent: US 7,778,169 B2
• Time in Patent Office: Days
• US Class Current: 370/412
• CPC Class Codes: H04L 12/43 with synchronous transmission, e.g. time division multiplex [TDM], slotted rings
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/283 in response to processing delays, e.g. caused by jitter or round trip time [RTT]
• CPC Class Codes: H04L 49/90 Buffering arrangements
• CPC Class Codes: H04L 49/9023 for implementing a jitter-buffer
• CPC Class Codes: H04L 49/9094 Arrangements for simultaneous transmit and receive, e.g. simultaneous reading/writing from/to the storage element
• CPC Class Codes: H04W 28/06 Optimizing the usage of the radio link, e.g. header compression, information sizing , discarding information system modifying transmission characteristic according to link quality by modifying frame length H04L1/0007; dynamic adaptation of the packet size for flow control or congestion control H04L47/365
• CPC Class Codes: H04W 28/14 using intermediate storage
• CPC Class Codes: H04W 74/04 Scheduled access hybrid access H04W74/02

Abstract

Media that is normally packetized into many separate individual packets and then queued for individual transmission during a transmit window is combined together into one, or a few, packets. The larger packets more efficiently carry media over a time slotted communication media since only one, or a few, packet headers are used for carrying a larger amount of media. Since packets cannot be transmitted until the start of a new transmit window, the larger packets do not substantially add to the overall packet delay that normally occurs when larger packets are formatted and transmitted in non-time slotted networks. In another aspect of the system, probe packets are used to identify the start of the transmit window. The transmit window start time is inferred from the round trip times for the probe packets and media packetization is then synchronized with the identified transmit windows.

Claims

1. A method of transmitting packets over a slotted communication system, comprising:

combining all media queued while waiting for a transmit time slot into one, or a few, packets; and

sending the one or few packets during the transmit time slot.

2. The method according to claim 1 including combining at least all the media queued from an end of a previous time slot up to at least a beginning of a next transmit time slot into a single packet.

3. The method according to claim 2 including combining at least a portion of the media received during the previous transmit time slot and/or combining at least a portion of the media received during the next transmit time slot into the same packet.

4. The method according to claim 1 including sending at least one additional packet that contains additional media received during the time slot.

5. The method according to claim 1 including:

queuing probe packets during both transmit and receive time slots;

comparing round trip times for the probe packets; and

identifying the transmit time slots according to the round trip time comparisons.

6. The method according to claim 5 including identifying when round trip times for the probe packets spike from a relatively short round trip time to a relatively large round trip time as an end of a transmit time slot and using the identified end of the transmit time slot to determine what media to combine into a same packet.

7. The method according to claim 1 including receiving the one or few combined media packets during a receive time slot.

8. A media packetizer, comprising:

a processor configured to combine media into a same packet according to an amount of media received while waiting for a next transmit window.

9. The media packetizer according to claim 8 wherein the processor combines queued media from at least an end of a last transmit window to at least a beginning of a next transmit window into the same packet.

10. The media packetizer according to claim 9 wherein the processor combines additional media received during the last transmit window and/or additional media received during the next transmit window into the same packet.

11. The media packetizer according to claim 9 wherein the processor combines other media received during the last transmit window or during the next transmit window into another packet.

12. The media packetizer according to claim 8 including a satellite access device coupled to the processor for sending the packets during the transmit window.

13. The media packetizer according to claim 12 wherein the satellite access device identifies a transmit window time to the processor and the processor then synchronizes the amount of media combined in the same packet with the transmit window time.

14. The media packetizer according to claim 8 wherein the processor operates in a media source device, network processing device, or satellite access device that combines audio data queued during non-transmit windows into a same voice packet.

15. The media packetizer according to claim 8 including a satellite receiver that synchronizes media packetization with a satellite transmitted global time clock.

16. The media packetizer according to claim 8 wherein the processor queues individual probe packets during an entire transmit and receive cycle for a slotted communication system and then identifies the transmit window by comparing the round trip times for the received probe packets.

17. The media packetizer according to claim 16 wherein the processor identifies an end of the transmit window by detecting a sharp increase in the probe packet round trip times and uses the identified end of the transmit window to infer the start time for the transmit window.

18. A method for synchronizing with a time slotted communication system, comprising:

queuing probe packets during both transmit time slots and receive time slots;

identifying when the probe packets are queued;

identifying when the probe packets are received back;

identifying round trip times from when the probe packets are queued to when the probe packets are received back; and

identifying the transmit or receive time slots by comparing the round trip times for the different probe packets.

19. The method according to claim 18 including:

transferring the probe packets to a satellite access device;

identifying output times when the probe packets are transferred to the satellite access device;

identifying receive times when the probe packets are received back from the satellite access device;

determining round trip times for the probe packets according to the identified output times and receive times; and

inferring when the transmit time slots are open according to the determined round trip times.

20. The method according to claim 19 including inferring when the transmit window ends by identifying when the round trip times for the probe packets spike from having a shortest round trip time to a longest round trip time.

21. The method according to claim 18 including combining media queued for transmission during a next transmit window into a same media packet and sending the media packet during the next transmit window.

22. A system for transmitting packets over a slotted communication system, comprising:

means for combining all media queued while waiting for a transmit time slot into one, or a few, packets; and

means for sending the one or few packets during the transmit time slot.

23. The system according to claim 22 including means for combining at least all the media queue from an end of a previous time slot up to at least a beginning of a next transmit time slot into a single packet.

24. The system according to claim 23 including means for combining at least a portion of the media received during the previous transmit time slot and/or combining at least a portion of the media received during the next transmit time slot into the same single packet.

25. The system according to claim 22 including means for sending at least one additional packet that contains additional media received during the time slot.

26. The system according to claim 22 including:

queuing probe packets during both transmit and receive time slots;

comparing round trip times for the probe packets; and

identifying the transmit time slots according to the round trip time comparisons.

27. A computer readable medium containing computer executable instructions for transmitting packets over a slotted communication system, the instructions when executed:

combining all media queued while waiting for a transmit time slot into one, or a few, packets; and

sending the one or few packets during the transmit time slot.